Study On The Microwave Assistant Synthesis And Performance Of The Perovskite-type Oxides

The emissions of CO2 and other greenhouse gases cause global warming, and carbon emission reduction becomes urgent demand. Oxyfuel combustion technology can help reduce carbon emissions on a large scale, but the high oxygen cost has restricted its development. A new method which uses perovskite-type oxygen carrier and CO2 in recycled flue gas to produce an O2-enriched CO2 stream is proposed. In order to get a perovskite-type oxide which has good oxygen release performance and stable structure, through improving the microwave-assisted soo-gel method, a new series of Ba-Co-O perovskite-type oxygen carriers have been successfully synthesized, meanwhile, the fixed bed experiment?X-ray diffraction analysis and scanning electron microscopy were performed to study the reaction properties and cycle characteristics of synthetic perovskite oxygen carrier. The main experimental contents and conclusions are as follows:The results of fixed bed experiment show that A-bite/B-bite replacing and doping make a great influence on the oxygen release performance of perovskite-type oxygen carrier. According to A-site doping, bigger ionic radius and smaller ionic potential of alkaline earth metal ion like Ba should be taken into account, and B-site shoud consider variable valency and smaller ionic potential ion like Co, then, BaCoO3-? exhibited excellent oxygen desorption performance among the synthesized samples. Fresh BaCoO3-? samples are perovskite structure and have many gaps; samples mainly become BaCO3, Co3O4 and CoO with little gap after the reaction.The optimal adsorption temperature and desorption temperature for the reaction of BaCoO3-? and CO2 are all 850 ?, the quantity of released oxygen first increases then decreases with the increase of reaction temperature; The longer the adsorption time of oxygen, the more oxygen samples release. Reaction pressure makes a great influence, and oxygen desorption quantity almost linearly increases with the pressure.Orthogonal experiments show that the best conditions of microwave-assisted soo-gel method to synthesis perovskite-type oxygen carriers are precursor pH 8?microwave time 25 min?microwave power 77% and calcination temperature 500 ?, besides, the primary and secondary order of these factors: pH>microwave time>calcination temperature>microwave power. All samples from orthogonal experiments are perovskite phase, the precursor of partial acidic or strong alkaline is not conducive for the growth of perovskite crystal. Long time microwave?high power microwave or high temperature calcination would lead to the samples sintered. The cyclic performance of BaCoO3-? is good, and the samples have little change after the cycle. Therefore, BaCoO3-? can produce an stable O2-enriched CO2 stream for oxyfuel combustion.